The long range objective of this research is to identify and understand the types of cellular interactions that bring about stereotyped axon growth and patterned synaptogenesis within the vertebrate CNS. The work uses microsurgical techniques and amphibian (Rana pipiens) material to manipulate the developing nervous system in ways that are simply not feasible with other vertebrates. Most of our present effort concentrates on a preparation where supernumerary eyes are implanted into host embryos. This produces animals in which 2 (or more) complete retinal projections converge on one tectal lobe. The invarient result is that the retinotopically organized inputs from each eye terminate in highly stereotyped eye-specific stripes. This pattern of afferent segregation is never seen in normal frogs but it is strikingly similar to the ocular dominance columns of cat and primate visual cortex. Experiments with three and four eyed frogs will use a variety of anatomical techniques and electrophysiology to ask: What effects does increased competition have on the retinal and tectal cells involved?; What is the relationship between retinotopic order, input segregation and visual activity? and, What determines the constant orientation and width of eye-specific bands? Answers to these questions should be generally applicable to the tissues of synaptic competition during neurogenesis and they could provide specific information on the synaptic interactions that produce amplyopia or loss of stereopsis with strabismus.